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Low voltage micro-network droop control method based on 'virtual complex impedance'

A virtual complex impedance, low-voltage micro-grid technology, applied in the direction of AC network circuits, electrical components, circuit devices, etc., can solve the problems of inverter power coupling enhancement, system stability reduction, voltage drop, etc., to reduce voltage drop. , improve power quality and achieve the effect of balanced control

Inactive Publication Date: 2019-03-19
HUNAN UNIV OF TECH
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Problems solved by technology

[0005] Aiming at the problem of low-voltage micro-grid or line impedance resistive system, high resistance-inductance ratio will strengthen the power coupling of the inverter and reduce the stability of the system. The introduction of traditional virtual impedance will cause the problem of voltage drop. A dynamic The virtual complex impedance control strategy is used to solve the problems that the conventional virtual impedance value cannot be selected and the line voltage drop is large

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  • Low voltage micro-network droop control method based on 'virtual complex impedance'
  • Low voltage micro-network droop control method based on 'virtual complex impedance'
  • Low voltage micro-network droop control method based on 'virtual complex impedance'

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[0044] The implementation of the present invention will be described in detail below in conjunction with the accompanying drawings.

[0045] Such as Figure 1-11As shown, a low-voltage microgrid droop control method based on "virtual complex impedance" includes the following steps:

[0046] S1. Analyzing the problem of large voltage drop caused by the introduction of traditional virtual impedance, the droop control method with resistance sense is adopted, and the expression is:

[0047] f-f 0 =-m(P-P 0 )+rn(Q-Q 0 ) (1)

[0048] u 1 -U 0 =-rm(P-P 0 )-n(Q-Q 0 ) (2)

[0049] Among them, m, n are the droop coefficients, r is the line resistance-inductance ratio, and r=R / X, f 0 is the reference frequency of the system, U 0 is the system reference voltage, P 0 , Q 0 The reference value of active power and reactive power, by adjusting m, n and r, can compensate the fluctuation deviation of inverter output frequency and voltage amplitude, when r=0, the above formula is th...

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Abstract

The invention discloses a low voltage micro-network control policy based on 'virtual complex impedance'. The method comprises the steps that the introduction of traditional virtual impedance causes alarge voltage drop; a general droop control expression with a resistance ratio is proposed; virtual complex impedance is designed; the expression of virtual complex impedance is constructed to acquirethe virtual complex impedance expression related to the resistance ratio r; a photovoltaic grid-connected inverter mathematical model with virtual complex impedance is established; the output voltageand equivalent output impedance of an inverter are acquired; a virtual impedance value is set according to the total voltage drop of a system; and the new voltage value of the inverter is acquired. According to the invention, adaptive virtual impedance is used to adjust the equivalent output impedance of the micro-network parallel inverter, so that the impedance tends to be inductive; the virtualimpedance can be adaptively adjusted, which not only reduces voltage drop, but also achieves power equalization control; power coupling is reduced; and the power quality of a micro-source during operation is improved.

Description

technical field [0001] The invention relates to a low-voltage micro-grid control strategy, in particular to a low-voltage micro-grid control strategy based on "virtual complex impedance". Background technique [0002] In recent years, microgrid has gradually become a hot research focus at home and abroad due to its diversified energy supply modes and flexible control methods. Conventional droop control methods are mainly applied to high-voltage transmission lines with small resistance-to-inductance ratio (R / X). At this time, the equivalent output impedance of each parallel inverter is purely inductive, and the active power P pair and reactive power Q The relationship between the voltages U is almost decoupled. However, in a low-voltage microgrid or a system with resistive line impedance, a high resistance-to-inductance ratio will strengthen the power coupling of the inverter and reduce system stability, making it difficult to achieve effective control of power quality. In ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J3/00
CPCH02J3/00H02J2203/20
Inventor 李圣清李静萍
Owner HUNAN UNIV OF TECH
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